Maize transcription factor ZmEREB167 negatively regulates starch accumulation and kernel size.

Abstract

Transcription factors play critical roles in the regulation of gene expression during maize kernel development. The maize endosperm, a large storage organ, accounting for nearly 90% of the dry weight of mature kernels, serves as the primary site for starch storage. In this study, we identify an endosperm-specific EREB gene, ZmEREB167, which encodes a nucleus-localized EREB protein. Knockout of ZmEREB167 significantly increases kernel size and weight, as well as starch and protein content, compared with the wild type. In situ hybridization experiments show that ZmEREB167 is highly expressed in the BETL as well as PED regions of maize kernels. Dual-luciferase assays show that ZmEREB167 exhibits transcriptionally repressor activity in maize protoplasts. Transcriptome analysis reveals that a large number of genes are up-regulated in the Zmereb167-C1 mutant compared with the wild type, including key genetic factors such as ZmMRP-1 and ZmMN1, as well as multiple transporters involved in maize endosperm development. Integration of RNA-seq and ChIP-seq results identify 68 target genes modulated by ZmEREB167. We find that ZmEREB167 directly targets OPAQUE2, ZmNRT1.1, ZmIAA12, ZmIAA19, and ZmbZIP20, repressing their expressions. Our study demonstrates that ZmEREB167 functions as a negative regulator in maize endosperm development and affects starch accumulation and kernel size.